Transformation Of Carbamazepine Research Articles

Optimisation of treatment efficiency and effluent toxicity during carbamazepine degradation via electrochemical oxidation

The commercialisation of electrochemical advanced oxidation processes (eAOPs) as a method for removing recalcitrant pollutants from wastewater is currently limited due to the potential for the formation of toxic by-products. In this regard, this research comprised a comprehensive optimisation study aimed at finding a balance between minimising the toxicity effects observed via phytotoxicity assays and maximising the eAOP degradation efficiency under low energy requirements. To this end, carbamazepine (CBZ) was selected as the target pollutant in synthetic wastewater, and the operating conditions considered for optimisation were the nature of the anolyte (i.e., sulfate- or chloride-based), its concentration, and the current density applied. Together with the identification of the CBZ transformation products and their estimated toxicity based on the ECOSAR model, the optimum treatment was found to correspond to the degradation in 500 mg L−1 of a sulfate-based anolyte at a current density of 10 A m−2. These conditions led to the fewest and least toxic transformation products and favoured plant growth indices in phytotoxicity tests. Even if additional process improvements are required to reduce effluent toxicity, continuing such a multi-target optimisation approach can lead to innocuous electrochemical wastewater treatment.

Degradation and transformation of carbamazepine in aqueous medium under non-thermal plasma oxidation process

Carbamazepine (CBZ) is a pharmaceutical compound detected in various water resources. With a view to removing this contaminant, the applicability of non-thermal plasma (NTP) oxidation process has been widely tested in recent years. This study utilized NTP from a dielectric barrier discharge reactor in the treatment of CBZ. NTP on the surface of a water sample containing 25 mg.L−1 of CBZ resulted in a removal efficiency of over 90% with an energy yield of 0.19 g. (kWh)−1. On the other hand, a rapid reduction in pH and an increase of conductivity and nitrate/nitrite ions concentration were observed during the degradation. The applied voltage amplitude significantly affected the removal efficiency and the energy yield as the degradation efficiency was 55%, 70%, and 72% respectively with an applied voltage of 8, 10, and 12 kV. The water matrices containing inorganic anions such as chloride and carbonate ions reduced the removal efficiency by scavenging the reactive species. Accordingly, a reduction in the removal efficiency was observed in tap water. The high-resolution mass spectrometry (HRMS) results revealed that both reactive oxygen and nitrogen species take part in the reaction process which yields many intermediate products including aromatic nitro-products. This study concluded that NTP can effectively degrade CBZ in both pure and tap water, but special attention must be paid to changes in the water quality parameters (pH, conductivity, and nitrate/nitrite ions) and the fate of nitro products.

Synthesis and characterization of new hybrid decatungstate anions (CTAB)4W10O32 : toward heterogeneous photocatalysis

ABSTRACT In the present study, hybrid decatungstate based photocatalysts, [(C16H33)N(CH3)3]4[W10O32], were synthesized through the reaction of hexadecyltrimethylammonium surfactant (CTAB) and sodium decatungstate Na4W10O32.2.6 H2O (W10) using different molar ratios of W10:CTAB (1:1 for compound 1 and 1:3 for compound 2) under aqueous conditions. The characterization of these hybrid materials was carried out using FT-IR spectroscopy, UV-visible spectroscopy, TGA, XRD and SEM, which confirmed the formation of [(C16H33)N(CH3)3]4[W10O32] materials. The influences of the molar ratio on the bandgap energy, photocatalytic activity and material morphology were compared and discussed in detail. FT-IR Spectroscopy indicates that CTAB reacted with W10, producing an insoluble product in aqueous media as expected. UV-Visible spectroscopy revealed that the hybrid material with a low amount of CTAB absorbed in the visible area compared to the other one, with the optical bandgap decreasing to 2.42 eV for compound 1 in particular. The UV-visible photocatalytic degradation of carbamazepine (CBZ) in aqueous solution demonstrated the efficiency of both compounds with approximately 46 and 88% of CBZ transformation after 7 hours of exposure for compound 1 and 2, respectively. These results prove that the new hybrid decatungstate has effective photocatalytic activity, which depends on the synthesis conditions.

Synergistic effect of nitrate on UV-chlorine photochemical degradation of carbamazepine.

We investigated the use of UV-chlorine advanced oxidation process for the removal and transformation of carbamazepine (CBZ), and its photochemical synergy with NO3- for the production of .OH towards enhancing CBZ removal in aqueous solution. Production of .OH by UV-chlorine system with/without NO3- was studied under different conditions, by using salicylic acid (SA) as the chemical probe for .OH. Initial concentration of 30 mg/L SA, 5 and 10 mg/L chlorine, and 0-10 mg/L NO3- under irradiation at 254 nm (3.026 W/L) in a photochemical reactor was used. Aqueous solutions containing 10 mg/L chlorine and spiked with 4 mg/L NO3- gave the highest reproducible generation of .OH. Using initial concentrations of 10 mg/L CBZ and 10 mg/L chlorine, 60 % CBZ was removed after 10 min of irradiation without NO3-, while 72 % CBZ was removed with 4 mg/L NO3- added. There was no noticeable CBZ removal after 10 min of irradiation in the presence of NO3- without chlorine. Corresponding dark reactions were also conducted, with no noticeable degradation of CBZ. Samples were analyzed via UHPLC, LC-MS, and TOC (total organic carbon) analyzer for CBZ and TOC concentrations respectively. Although, there was significant reduction in CBZ concentrationduring both photochemical degradation processes, the was low TOC removal (~10%) in each case. The two photochemical degradation processes also seem to generate similar degradation products indicating that the addition NO3- of the UV-chlorine process might not have changed the degradation mechanism. The results indicate that NO3- could act synergistically in a UV-chlorine system to increase CBZ removal and reduce the quantity of free chlorine required to achieve a target removal efficiency. This could facilitate reduction in the potential production of chlorinated byproducts in the system.

Removal and fate of carbamazepine in the microbial fuel cell coupled constructed wetland system

Carbamazepine (CBZ), which is difficult to remove in the wastewater treatment system and easily forms toxic transformation products during the treatment process, is one of the priority pollutants of pharmaceuticals and personal care products (PPCPs). Increasing attention has been paid to explore their treatment technology without side effects from the treatment products. This study aims to reveal the removal and transformation of CBZ in the microbial fuel cell coupled constructed wetland (CW-MFC) system. The CW-MFC system was operated continuously at room temperature for nearly 80 days. The results show that CW-MFC system can effectively remove CBZ with an average removal rate of 97%. Three transformation products were identified by liquid chromatography−high-resolution mass spectrometry: 2-(2-oxoquinazolin-1(2H)-yl) benzoic acid (TP267), methyl 2-(2-oxoquinazolin-1(2H)-yl) benzoate (TP281), 2-(2,4-dioxo-3,4-dihydroquinazolin-1(2H)-yl) benzoic acid (TP283). Except TP281 in the influent, the other transformation products were formed in the system, which indicated that TP267 and TP283 were the main transformation products of CBZ. The formation pathway of transformation products could be explained by reactions including oxidation, hydrolysis, bond rupture and intramolecular reaction. The results also indicate that the CW-MFC system might be a promising technology for PPCPs treatment.

Carbamazepine degradation by heterogeneous activation of peroxymonosulfate with lanthanum cobaltite perovskite: Performance, mechanism and toxicity

The widely used carbamazepine (CBZ) is one of the most persistent pharmaceuticals and suffers insufficient removal efficiency by conventional wastewater treatment. A synthesized Co-based perovskite (LaCoO3) was used to activate peroxymonosulfate (PMS) in order to degrade CBZ. Results showed that LaCoO3 exhibited an excellent performance in PMS activation and CBZ degradation at neutral pH, with low cobalt leaching. The results of FT-IR and XPS verified the high structurally and chemically stability of LaCoO3 in PMS activation. Electron spin resonance (ESR) analysis suggested the generation of radical species, such as sulfate radicals (SO4-) and hydroxyl radicals (OH). Radical quenching experiments further revealed the responsibility of SO4- as the dominant oxidant for CBZ oxidation. Ten products were detected via the oxidation of CBZ, with the olefinic double bond attacked by SO4- as the initial step. Hydroxylation, hydrolysis, cyclization and dehydration were involved along the transformation of CBZ. The toxicity of CBZ solution was significantly reduced after treating by PMS/LaCoO3.

Modeling the Translocation and Transformation of Chemicals in the Soil‐Plant Continuum: A Dynamic Plant Uptake Module for the HYDRUS Model

AbstractFood contamination is responsible for thousands of deaths worldwide every year. Plants represent the most common pathway for chemicals into the human and animal food chain. Although existing dynamic plant uptake models for chemicals are crucial for the development of reliable mitigation strategies for food pollution, they nevertheless simplify the description of physicochemical processes in soil and plants, mass transfer processes between soil and plants and in plants, and transformation in plants. To fill this scientific gap, we couple a widely used hydrological model (HYDRUS) with a multicompartment dynamic plant uptake model, which accounts for differentiated multiple metabolization pathways in plant's tissues. The developed model is validated first theoretically and then experimentally against measured data from an experiment on the translocation and transformation of carbamazepine in three vegetables. The analysis is further enriched by performing a global sensitivity analysis on the soil‐plant model to identify factors driving the compound's accumulation in plants' shoots, as well as to elucidate the role and the importance of soil hydraulic properties on the plant uptake process. Results of the multilevel numerical analysis emphasize the model's flexibility and demonstrate its ability to accurately reproduce physicochemical processes involved in the dynamic plant uptake of chemicals from contaminated soils.

Assessment of Biopharmaceutical Performance of Supersaturating Formulations of Carbamazepine in Rats Using Physiologically Based Pharmacokinetic Modeling.

There is an overgrowing emphasis on supersaturating drug delivery systems (SDDS) with increase in number of poorly water-soluble compounds. However, biopharmaceutical performance from these formulations is limited by phase transformation to stable crystalline form due to their high-energy physical form. In the present study, in vitro kinetic solubility in water and dissolution in biorelevant medium integrated with in silico physiologically based pharmacokinetic (PBPK) modeling was used to predict biopharmaceutical performance of SDDS of poorly water-soluble compound, carbamazepine (CBZ). GastroPlus™ with advanced compartmental absorption and transit model was used as a simulation tool for the study. Wherein, the model was developed using physicochemical properties of CBZ and disposition parameters obtained after intravenous administration of CBZ (20mg/kg) into Sprague-Dawley (SD) rats. Biorelevant medium was selected by screening different dissolution media for their capability to predict oral plasma concentration-time profile of marketed formulation of CBZ. In vivo performance of SDDS was predicted with the developed model and compared to observed plasma concentration-time profile obtained after oral administration of SDDS into SD rats (20mg/kg). The predictions, with strategy of using kinetic solubility and dissolution in the selected biorelevant medium, were consistent with observed biopharmaceutical performance of SDDS. Additionally, phase transformation of CBZ during gastrointestinal transit of formulations was evaluated and correlated with in vivo dissolution deconvoluted by Loo-Reigelman analysis.

Fe(III)-citrate enhanced sunlight-driven photocatalysis of aqueous Carbamazepine

We investigated the effect of Fe(III)-citrate complexes on the photodegradation of Carbamazepine (CBZ) upon 365 nm irradiation in aqueous solution. A preliminary study of a {CBZ/Fe(III)-citrate} mixture in the dark and at room temperature showed no evidence of reaction. CBZ degradation efficiency depends on the pH of the medium, an effect attributed mainly to the speciation of Fe(III)-citrate. The influence of [CBZ] or [Fe(III)-citrate] on the kinetics of the reaction was studied. The reaction is biphasic, the first stage ends after ca. fifteen minutes and accounts for the major percentage of degradation. The presence of Fe(III)-citrate complex largely enhances the formation of Fe2+ and HO radicals; they form at the same rate at the beginning of the reaction. Increasing [O2] improved the degradation rate, and the use of i-PrOH as a scavenger confirmed the participation of HO in CBZ photodegradation. CBZ photodegradation was also studied under natural sunlight showing a degradation only slightly lower than under artificial light. HPLC/MS analysis confirmed 11% yield epoxycarbamazepine as the only reaction product observable with this technique after 180 min irradiation. An appropriate mechanism is proposed for CBZ transformation. CBZ phototransformation reached 65% at pH = 6.24, 87% at pH = 4.30 and ca. 100% at pH = 2.86 after 180 min upon 365 nm irradiation and the mineralization efficiency reaches 70% of TOC removal after 6 h of treatment. Our evidences show the epoxide photoproduct is just an intermediate that further reacts towards mineralization. This work highlights the important role of Fe(III)-carboxylate complexes may have on the fate of persistent organic pollutants in aquatic environments when irradiated with UV-A light.

Experiments and numerical simulation on the degradation processes of carbamazepine and triclosan in surface water: A case study for the Shahe Stream, South China

We examined the occurrence and fate of pharmaceuticals and personal care products in surface water by combining laboratory experiments with numerical simulations. The degradation processes of two typical PPCPs (triclosan and carbamazepine) collected from the Shahe Stream were studied. Hydrolysis, biodegradation, and photolysis were the three major routes of triclosan (TCS) and carbamazepine (CBZ) degradation. A central composite design method was used to investigate the effects of related natural parameters (including pH, dissolved oxygen, salinity, temperature, light intensity, and humic acid) on the TCS and CBZ degradation processes in the laboratory. Our results showed that the main degradation pathway of CBZ and TCS was direct photolysis during the daytime and that the maximal biodegradation rates of CBZ and TCS occurred at 22 °C when the optimum temperature function was used. Based on our experimental results, the observed degradation of CBZ and TCS followed pseudo-first-order kinetics, and the degradation kinetic equations under the influence of multiple natural parameters were established with estimated average degradation rate constants of 1.2452E−7 s−1 and 3.1260E−5 s−1 for CBZ and TCS, respectively. The degradation rate constants were incorporated into a one-dimensional, simply integrated hydrodynamic and water quality model. The proposed numerical model was applied to depict the transportation and transformation of CBZ and TCS in surface water and was validated by observational data from the Shahe Stream. The results showed that our model reproduced the observed patterns of CBZ and TCS concentrations reasonably, with slight overestimations compared to the observed data; the relative errors between the simulated and the observed concentrations were 5.85%–6.82% for CBZ and −156.85%–−7.18% for TCS. According to our simulation, the spatial distribution of TCS in surface water was determined by biochemical degradation processes that were most affected by temperature under natural conditions; in contrast, the distribution of CBZ was largely controlled by diffusion.

Application of a ceramic membrane contacting process for ozone and peroxone treatment of micropollutant contaminated surface water

This study investigates the performance of membrane-based ozonation and peroxone processes, regarding the transformation of carbamazepine (CBZ), benzotriazole (BZT), p-chlorobenzoic acid (pCBA) and atrazine (ATZ) in natural surface waters, as well as the formation of bromates. Ozonation, performed with the use of ceramic membrane contactor, was able to diminish CBZ concentration below 0.1 μM at 0.4 mg O3/mg DOC, i.e. presenting >90% removal rate, whereas the transformation of BZT, pCBA and ATZ was not exceeded 70%, 57% and 49%, respectively, under the same experimental conditions. The addition of H2O2 reduced the removal efficiency of CBZ, since up to -8% transformation values were observed at 0.1 mg O3/mg DOC. In contrast, the transformation of ozone-resistant compounds pCBA and ATZ was slightly improved by approximately 5–10%, at 0.8 mg O3/mg DOC. Membrane-based oxidative treatment of surface water resulted to high bromate concentrations (49 μg/L and 28 μg/L for ozone and peroxone process, respectively, at 0.8 mg O3/mg DOC). The results obtained by using the membrane contactor were also compared with the corresponding from conventional batch experiments. These results suggest that the implementation of membrane contactors with the highest possible inner surface per volume along with the use of low ozone gas concentration are required to improve the removal of micropollutants and diminish bromate formation.

Pharmacokinetics in Plants: Carbamazepine and Its Interactions with Lamotrigine.

Carbamazepine and lamotrigine prescribed antiepileptic drugs are highly persistent in the environment and were detected in crops irrigated with reclaimed wastewater. This study reports pharmacokinetics of the two drugs and their metabolites in cucumber plants under hydroponic culture, testing their uptake, translocation, and transformation over 96 h in single and bisolute systems at varying pH. Ruling out root adsorption and transformations in the nutrient solution, we demonstrate that carbamazepine root uptake is largely affected by the concentration gradient across the membrane. Unlike carbamazepine, lamotrigine is adsorbed to the root and undergoes ion trapping in root cells thus its translocation to the shoots is limited. On the basis of that, carbamazepine uptake was not affected by the presence of lamotrigine, while lamotrigine uptake was enhanced in the presence of carbamazepine. Transformation of carbamazepine in the roots was slightly reduced in the presence of lamotrigine. Carbamazepine metabolism was far more pronounced in the shoots than in the roots, indicating that most of the metabolism occurs in the leaves, probably due to higher concentration and longer residence time. This study indicates that the uptake of small nonionic pharmaceuticals is passive and governed by diffusion across the root membrane.

Transformation Products of Carbamazepine (CBZ) After Ozonation and their Toxicity Evaluation Using Pseudomonas sp. Strain KSH-1 in Aqueous Matrices.

Carbamazepine (CBZ) is an anti-epileptic and anti-convulsant drug widely used for the treatment of epilepsy and other bipolar disorders. Ozone as an advanced oxidation process has been widely used for the degradation of CBZ resulting in the formation of transformation products (ozonides). The present research aims to isolate and identify potential microorganism, capable of degradation of CBZ and its transformation products. The cell viability and cytotoxicity of pure CBZ and their ozone transformation products were evaluated using the cells of Pseudomonas sp. strain KSH-1 through cell viability assay tests. The cells metabolic activity was assessed at varying CBZ concentrations (~ 10-25ppm, pure CBZ) and cumulatively for ozone transformation products. For pure CBZ, % cell viability decreases as CBZ concentration increases, while, in case of post-ozonated CBZ transformation products, the viability decreases initially and then increases upon exposure of ozone with a maximum cell viability of 97 ± 2.8% evaluated for 2h post-ozonated samples.

Biotransformation of carbamazepine by laccase-mediator system: Kinetics, by-products and toxicity assessment

Abstract Carbamazepine (CBZ) is one of the most detected pharmaceutical compounds around the world, with adverse human and animal health impacts in wastewater effluents. Recently, biocatalytic degradation using ligninolytic enzymes such as laccase along with redox mediators provides a promising approach for their removal from water and wastewater. However, the effects of operational parameters on biotransformation need to be investigated in order to design a robust and efficient process. In this research, central composite design was performed and analyzed using response surface methodology to study the effects of temperature, pH, enzyme concentration and mediator concentration. The adequacy of the developed model was confirmed by the coefficient of multiple regression (R2 = 75.97%) indicating a reasonable model for practical implementation. The results showed that performing the biotransformation at 35 °C, pH 6, with 60 U/L of enzyme concentration and 18 μM of mediator concentration resulted in 95% removal of CBZ. 10,11-Dihydro-10,11-dihydroxy-CBZ and 10,11-dihydro-10,11-epoxy-CBZ were identified as the major metabolites of CBZ oxidation by laccase. The estrogenicity tests indicated that the CBZ with an initial concentration of 4 μM and its biotransformation products had no estrogenic effect. The successful transformation of CBZ demonstrated the potential of the laccase-mediator system for the removal of recalcitrant micro-contaminants.

Inhibition of the solid state transformation of carbamazepine in aqueous solution: impact of polymeric properties

The effects of polymers on the anhydrate-to-hydrate transformation of carbamazepine (CBZ) was investigated. The three types of polymers studied were polyvinylpyrrolidone (PVP), polyvinyl alcohol (PVA) and substituted celluloses which included hydroxypropyl methylcellulose (HPMC) and methylcellulose (MC). Anhydrous CBZ was added to dilute aqueous polymer solutions and Raman spectroscopy measurements were collected to monitor the kinetics of the solution-mediated transformation to CBZ dihydrate. Polymers exhibiting the greatest inhibition were able to reduce the growth phase of the solution-mediated transformation and change the habit of the hydrate crystal indicating polymer adsorption to the hydrate crystal surface as the mechanism of inhibition. The results of the various polymers showed that short chain substituted celluloses (HPMC and MC) inhibited the CBZ transformation to a much greater extent than longer chains. The same trend was observed for PVP and PVA, but to a lesser extent. These chain length effects were attributed to changes in polymer confirmation when adsorbed on the crystal surface. Additionally, decreasing the percentage of hydroxyl groups on the PVA polymer backbone reduced the ability of the polymer to inhibit the transformation and changing the degree of substitutions of methyl and hydroxypropyl groups on the cellulosic polymer backbone had no effect on the transformation.

Extensive Transformation of the Pharmaceutical Carbamazepine Following Uptake into Intact Tomato Plants.

Carbamazepine (CBZ) is an antiepileptic drug which is persistent in wastewater treatment plants and the environment. It has been frequently detected in plant material after irrigation with treated wastewater. To date, little information is, however, available on the transformation of CBZ in plants. In the present study, the uptake, translocation, and transformation of CBZ was studied in hydroponically grown tomato plants. After 35 days of exposure >80% of the total spiked amount of CBZ was taken by the tomato plants and mainly stored in the leaves. A total of 11 transformation products (TP) (mainly phase-I) were quantified by liquid chromatography-tandem mass spectrometry (LC-MS/MS) and their total amount corresponded to 33% of the CBZ taken up. The ratio of CBZ metabolites to CBZ was highest in fruits (up to 2.5) and leaves (0.5), suggesting an intensive transformation of CBZ in these compartments. Further 10 TPs (phase-I and II) were identified by LC-high resolution mass spectrometry screening, likely comprising another 12% of CBZ. On the basis of these experiments and on an experiment with CBZ-10,11-epoxide a transformation pathway of CBZ in intact tomato plants is proposed that involves epoxidation, hydrolysis, hydroxylation, ring contraction, or loss of the carbamoyl group, followed by conjugation to glucose or cysteine, but also reduction of CBZ. This transformation pathway and analytical data of CBZ transformation products allow for their determination also in field grown vegetable and for the generation of more accurate exposure data of consumers of vegetable irrigated with treated municipal wastewater.

Investigating natural attenuation of pharmaceuticals through unsaturated column tests

The growing consumption of pharmaceuticals together with their incomplete removal in wastewater treatment plants (WWTPs) implies the occurrence of these compounds in natural water resources. To investigate the natural attenuation of selected pharmaceuticals (caffeine, acetaminophen, sulfamethoxazole, naproxen and carbamazepine) during vadose zone infiltration, unsaturated column (L 26.67 cm, Ø 7.62 cm) experiments, filled with a sandy-loamy soil, were performed using two input concentrations (100 and 1000 μg L−1). The software Hydrus 1D was used to simulate experimental data. Caffeine and acetaminophen were never detected at the column outlet indicating a low environmental concern. On the other hand, attenuation of the detected pharmaceuticals could be reproduced by a combination of retardation and removal approaches. Carbamazepine is among the selected contaminants the most persistent. A dependence of removal rates on input concentrations was detected for sulfamethoxazole (μw from 2.78 d−1 to 1.16 d−1) and naproxen (μw from 1.16 d−1 to 0.63 d−1) attributed mainly to decreased metabolism of microorganisms when a higher input concentration is applied. Two transformation products (TPs) (N4-Acetylsulfamethoxazole and epoxycarbamazepine) derived from sulfamethoxazole and carbamazepine transformation, respectively, were detected during the experiment with the highest input concentration.

Reductive transformation of carbamazepine by abiotic and biotic processes

The antiepileptic drug carbamazepine (CBZ) is ubiquitously present in the anthropogenic water cycle and is therefore of concern regarding the potable water supply. Despite of its persistent behavior in the aquatic environment, a redox dependent removal at bank filtration sites with anaerobic aquifer passage was reported repeatedly but not elucidated in detail yet. The reductive transformation of CBZ was studied, using abiotic systems (catalytic hydrogenation, electrochemistry) as well as biologically active systems (column systems, batch degradation tests). In catalytic hydrogenation CBZ is gradually hydrogenated and nine transformation products (TPs) were detected by liquid chromatography high-resolution mass spectrometry. 10,11-Dihydro-CBZ ((2H)-CBZ) was the major stable product in these abiotic, surface catalyzed reduction processes and turned out to be not a precursor of the more hydrogenated TPs. In the biotic reduction processes the formation of (2H)-CBZ alone could not explain the observed CBZ decline. There, also traces of (6H)-CBZ and (8H)-CBZ were formed by microbes under anaerobic conditions and four phase-II metabolites of reduced CBZ could be detected and tentatively identified. Thus, the spectrum of reduction products of CBZ is more diverse than previously thought. In environmental samples CBZ removal along an anaerobic soil passage was confirmed and (2H)-CBZ was determined at one of the sites.

Photocatalytic degradation of antiepileptic drug carbamazepine with bismuth oxychlorides (BiOCl and BiOCl/AgCl composite) in water: Efficiency evaluation and elucidation degradation pathways

Abstract The heterogeneous photocatalytic degradation of carbamazepine (CBZ) was investigated in the presence of BiOCl/AgCl composite photocatalyst under simulated sunlight irradiation in water. BiOCl/AgCl composite showed higher photocatalytic activity than pure BiOCl for CBZ degradation. The photocatalytic mechanism analysis was based on byproducts identification by LC–MS-QTof and active species trapping or inhibiting experiments. The results revealed that the first step of the transformation mainly results in an electron transfer implying positive holes and to a lesser extent in hydroxyl radical’s involvement. The enhanced photocatalytic performance of BiOCl/AgCl was proved to be related to the suitable conduction and valence band interaction that extends optical response range but also improves the efficient separation of photoinduced electron-hole pairs. BiOCl/AgCl composite totally removed CBZ from natural surface water after 30 min irradiation, suggesting its potential application to wastewater treatments. Eight intermediate products were identified demonstrating that CBZ transformation occurs through two main routes from CBZ radical cation, hydroxylation of ring (aromatic or seven membered rings), followed by further oxidation, rearrangement ring and hydroxylation.

Increased dissolution rates of carbamazepine – gluconolactone binary blends processed by hot melt extrusion

Carbamazepine (CBZ) shows a poor dissolution, therefore, it is important to enhance its dissolution in GI tract to improve its bioavailability. In the present study, a new hydrophilic carrier, d-gluconolactone (GNL), was extruded with CBZ at various molar ratios to produce granules by using hot melt extrusion (HME) processing. The granular extrudates were characterised by X-ray powder diffraction, differential scanning calorimetry and hot stage microscopy to determine the solid state of CBZ. It was found that bulk CBZ (Form-III) transformed to the polymorphic Form-I during the HME processing. GNL was proved to be an efficient carrier for CBZ to enhance the dissolution rate. The increase in the dissolution rate was observed for both physical mixtures and the extrudates of CBZ-GNL. However, the extrudates showed faster dissolution rates compared to physical mixtures in an ascending order of 2:1 < 1:1 < 1.5:1 (CBZ:GNL). The increase in the dissolution rates was attributed to the transformation of CBZ III to Form-I and also to the increased drug wettability/solubilisation in the presence of the carrier.